Method for fixing or separating ions, in particular of lead, using per(3,6-anhydro)cy-clodextrin derivatives

ABSTRACT

The invention relates to the fixation or separation of ions, particularly of Pb, by per(3,6-anhydro)cylcodextrin derivatives. 
     This can be carried out by contacting the medium containing the ions to be fixed or separated, with a per(3,6-anhydro)cylcodextrin derivative of formula:                    
     in which at least one of the R 1  represents OCH 3 , whilst the other R 1  can represent OCH 3 , OH or other groups, for complexing the ions. 
     Preferably, for the fixation of lead, the derivative complies with formula (I) with n=6 and all the R 1 =OCH 3 .

TECHNICAL FIELD

The present invention relates to a process for the fixation orseparation of ions, particularly of Pb, by per(3,6-anhydro)cylcodextrinderivatives.

PRIOR ART

Cyclodextrins or cyclomaltooligosaccharides are compounds having anatural origin formed by the linking of glucose units which areα(1,4)-bonded.

Numerous works have revealed that these compounds could form inclusioncomplexes with hydrophobic molecules, thus permitting theirsolubilization in aqueous media. Numerous applications have beenproposed for taking advantage of this phenomenon, particularly in thepharmaceutical field, as is described by D. Duchêne “Pharmaceuticalapplication of cyclodextrins” in “Cyclodextrins and their industrialuses”, D. Duchêne, Editions de Santé, Paris, 1987, pp 213-257.

Pharmaceuticals have already been marketed in Japan, Italy and morerecently in France, in the form of complexes in cyclodextrins. InFrance, the first active principle marketed in the form of an inclusioncomplex in a cyclodextrin is piroxicam, which is an anti-inflammatoryagent marketed by Pierre Fabre Medicament under the name BREXIN^((R)).Among the very numerous modified derivatives of said cyclodextrins,those for which the cavity is turned on itself have interestingproperties, even though their capacity to include organic molecules islost or very limited. Compounds of this type areper(3,6-anhydro)cyclodextrins.

The synthesis of said peranhydrocyclodextrins has been described as from1991 in document 1: Gadelle A. and Defaye J., Angew. Chem. Int. Ed.Engl., 1991, 30, 78-79; and document 2: Ashton P. R., Ellwood P., StatonI. and Stoddart J. F., Angew. Chem. Int. Ed. Engl., 1991, 30, 80-81) andit has been demonstrated that these derivatives have interestingsolubilities both in water and organic solvents. Several subsequentstudies (document 3: Yamamura H. and Fujita K. Chem. Pharm. Bull., 1991,39, 2505-2508; document 4: Yamamura H., Ezuka T., Kawase Y., Kawai M.,Butsugan Y. and Fujita K., J. Chem. Soc., Chem. Com., 1993, 636-637; anddocument 5: Yamamura H., Nagaoka H., Kawai M. and Butsugan Y.,Tetrahedron Lett. 1995, 36, 1093-1094) have also demonstrated that theseperanhydro derivatives could complex alkaline ions with a non-negligibleselectivity.

Ashton et al in J. Org. Chem., 60, 1995, pp 3898-3903, have describedthe synthesis of the pernanhydro-β-cyclodextrin derivative substitutedin the 2-position by a methyl group.

However, this chemical modification has not been carried out with a viewto optimizing the complexing or selectivity properties of theperanhydrocyclodextrins.

DESCRIPTION OF THE INVENTION

The present invention relates to the use for the separation or fixationof ions of derivatives of peranhydrocyclodextrins in which a chemicalmodification has been carried out for modifying their properties,particularly their selectivity with respect to the ions which they areliable to complex and in particular with respect to lead.

According to the invention, this modification relates to the hydroxylgroups present on said molecule, as well as the configuration of carbonC₂, which can be reversed for leading to L-mannose-type derivatives.

Thus, the invention relates to a process for the fixation or separationions, which consists of contacting a medium containing said ions with aderivative of per(3,6-anhydro)cyclodextrin, complying with one of thefollowing formulas:

in which at least one of the R¹ represents the methoxy group and theother R¹, which can be the same or different, represent a groupcomplying with one of the formulas: OH, OR², SH, SR², OCOR², NH₂, NR²R³,CONR²R³, CONH₂, CN, COOR², COOH and R², in which R² represents asaturated or unsaturated, aliphatic or aromatic, hydrocarbon group,which can have one or more heteroatoms chosen from among O, S and N, andR³ represents a hydrogen atom or a saturated or unsaturated, aromatic oraliphatic, hydrocarbon group, which can have one or more heteroatomschosen from among O, S and N, and n is equal to 6, 7 or 8, for fixingsaid ions in complex form with the per(3,6-anhydro)cyclodextrinderivative and for separating them from said medium.

In the cyclodextrin derivative of formula (I) or (II), the aliphatic oraromatic, hydrocarbon groups which can be used for R² and R³ can be ofvarious types. They are constituted by a carbon chain, in which certaincarbon atoms can be replaced by one or more heteroatoms such as O, S andN and can have one or more ethylene or acetylene unsaturations.Moreover, the hydrocarbon group can have different substituents, inparticular functional groups or halogen atoms. The aromatic hydrocarbongroups can be constituted by the optionally substituted tosyl group andphenyl group, e.g. by alkyl groups having 1 to 20 carbon atoms. R² andR³ can in particular represent a straight or branched, alkyl grouphaving 1 to 20 carbon atoms.

According to a preferred embodiment of the invention, intended moreparticularly for the separation of lead ions, theper(3,6-anhydro)cyclodextrin derivative is an β-cyclodextrin derivative,i.e. in the aforementioned formulas (I) and (II), n is equal to 6.

Preferably, the derivative used complies with formula (I), in which allthe R¹ represent the methoxy group and n is equal to 6.

The ions which can be fixed or separated by the process according to theinvention can be of various types. They can e.g. be ions of alkalimetals, actinides, lanthanides or polluting metals such as lead,mercury, cobalt and strontium.

The process according to the invention more particularly applies to theseparation and fixation of lead in complex form.

Thus, lead and its derivatives pollute the environment and are toxicboth to man and animal. The main toxic effects affect the neurologicaldevelopment and the functioning of the nervous system. It isconsequently necessary to separate and eliminate lead from theenvironment and store it safely.

In addition, products which would make it possible to ensure the leaddecontamination of living beings by preventing the action of lead on thenervous system and on other organs, would be of great interest forsolving these problems.

According to the invention, it has been found that derivatives ofper(3,6-anhydro)cyclodextrins complying with the above formulas (I) and(II), have a high specificity for lead and are capable of complexing itwith high yields able to reach 100%, even in the presence of other ions,such as sodium ions.

Thus, it is possible to separate the lead from the surrounding medium incomplex form.

The invention also relates to complexes of lead and derivatives ofper(3,6-anhydro)cyclodextrins of formulas (I) or (II) describedhereinbefore.

For implementing the process according to the invention, it is possibleto use the per(3,6-anhydro)cyclodextrin derivative of formula (I) or(II) in the form of an aqueous solution or organic solution.

When the medium containing the ions to be separated or fixed is anaqueous solution, it is possible to dissolve the cyclodextrin derivativein an organic solvent which is immiscible with the aqueous solution,e.g. in chloroform, in order to form the complex in the organic solutionand separate it easily from the aqueous solution.

It is also possible to use the cyclodextrin derivative in aqueoussolution, particularly for the lead decontamination of living beings.

Thus, it is known that cyclodextrin derivatives of formulas (I) or (II)are biocompatible compounds. They can consequently be administered toman or animals for ensuring the fixation of the lead in complex form andthus prevent its interaction with the organs of the human or animalbody.

The invention also relates to a pharmaceutical composition for the leaddecontamination of a living being, characterized in that it comprises aper(3,6-anhydro)cyclodextrin derivative complying with one of thefollowing formulas:

in which at least one of the R¹ represents the methoxy group and theother R¹, which can be the same or different, represent a groupcomplying with one of the formulas: OH, OR², SH, SR², OCOR², NH₂, NR²R³,CONR²R³, CONH₂, CN, COOR², COOH and R², in which R² represents asaturated or unsaturated, aliphatic or aromatic, hydrocarbon group,which can have one or more heteroatoms chosen from among O, S and N, andR³ represents a hydrogen atom or a saturated or unsaturated, aliphaticor aromatic, hydrocarbon group, which can have one or more heteroatomschosen from among O, S and N, and n is equal to 6, 7 or 8.

Preferably, the per(3,6-anhydro)cyclodextrin derivative used in thiscomposition complies with formula (I), in which all the R¹ represent themethoxy group and n is equal to 6.

This composition can be administered orally or by injection.

The aqueous solutions can incorporate up to 0.08 mole/l of thederivative of formula (I).

The administered quantities will depend on the lead contamination leveland the weight of the patient.

The invention also relates to per(3,6-anhydro)cyclodextrin derivatives,usable in this process and which comply with one of the followingformulas:

in which at least one of the R¹ represents the methoxy group and theother R¹, which can be the same or different, represent a hydrogen atomor a group complying with one of the formulas: OH, OR², SH, SR², OCOR²,NH₂, NR²R³, CONR²R³, CONH₂, CN, COOR², COOH and R², in which R²represents a saturated or unsaturated, aliphatic or aromatic,hydrocarbon group, which can have one or more heteroatoms chosen fromamong O, S and N, and R³ represents a hydrogen atom or a saturated orunsaturated, aliphatic or aromatic, hydrocarbon group, which can haveone or more heteroatoms chosen from among O, S and N, and n is equal to6, 7 or 8, provided that all the R¹ do not represent OCH₃ when n=7 andthat the derivative complies with formula (I).

The cyclodextrin derivatives used in the invention can be prepared bydifferent processes.

When the cyclodextrin derivative complies with the above formula (I) or(II), in which at least one of the R¹ represents the methoxy group, theother R¹ representing OH or OCH₃ and n is equal to 6, 7 or 8, they canbe prepared by a process having the following stages:

1) reacting a peranhydrocyclodextrin complying with one of the formulas:

 in which n is equal to 6, 7 or 8, with an alkali metal hydride forconverting the OH group or groups into OM group or groups with Mrepresenting an alkali metal,

2) reacting the modified peranhydrocyclodextrin obtained in 1), with amethyl halide of formula CH₃X, in which X represents a halogen atom and

3) if necessary, reacting the peranhydrocyclodextrin obtained in

2) with one or more reagents in order to substitute it by R¹ groupsdiffering from OCH₃.

For performing stage 2), use is made of the quantity of CH₃X necessaryfor modifying one or more of the OH groups of the cyclodextrin.

When the cyclodextrin derivative complies with the above formulas (I) or(II), in which the other R1 represent OR², with R² having the meaninggiven hereinbefore, except CH₃, the above procedure is adopted forintroducing the OCH₃ group or groups, followed by reacting thederivative with a halide of formula R₂X, in which R² has the meaninggiven hereinbefore and X is a halogen atom.

When the cyclodextrin derivative complies with formula (I) or (II), inwhich the other R¹ represent OCOR², the above procedure is adopted forfirst introducing the methoxy groups and then the methyl derivative isreacted with an acid anhydride or halide of formulas R₂COX or (R²CO)₂O,in which R² has the meaning given hereinbefore and X represents ahalogen atom, in order to replace the remaining hydroxyls by OCOR².

When it is wished to prepare a cyclodextrin derivative, in which theother R¹ represent a halogen atom or a group of formula SH, SR², NH₂,NR^(2R) ³, CONR²R³, CONH₂, CN, COOR², COOH, or R², with R² and R³ havingthe meanings given hereinbefore, and n is equal to 6, 7 or 8, it ispossible to carry out the following stages starting with a partlymethylated peranhydrocyclodextrin, i.e. in which at least one of the R¹represents OCH₃ and the other R¹ represent OH and performing thefollowing stages:

1) reacting said peranhydrocyclodextrin with an alkali metal hydride forconverting the OH group or groups into OM group or groups with Mrepresenting an alkali metal,

2) reacting the modified peranhydrocyclodextrin obtained in 1) with achloride of formula ClSO₂R² with R² having the meaning givenhereinbefore, for obtaining the derivative of formula (I) or (II), inwhich at least one of the R¹ is a group of formula OSO₂R² and

3) reacting the derivative obtained in the second stage with one or moreappropriate reagents for replacing OSO₂R² by the desired R¹ group.

In this process, the per(3,6-anhydro)cyclodextrin is firstly transformedinto alkoxide by the action of alkali metal hydride and said alkoxide isthen converted into a derivative having a starting group of formulaOSO₂R², which is then reacted in one or more stages with one or moreappropriate reagents for replacing said starting group by the desired R¹group.

Thus, in the case where R¹ has to represent NH₂, it is possible to reactN₃M and the compound defined in 2). The thus obtained compound, calledan azide, can undergo a catalytic hydrogenation or can be treated in thepresence of ammonia NH₃, in order to obtain the product where R¹ is torepresent NH₂.

The product where R¹ is to represent NR²R³ is obtained by reacting thecompound defined in 2) with the compound NHR²R³.

In the case where R¹ is to represent SH or SR², it is possible to reactthe compound defined in 2) with a halide X⁻, which gives the compoundwith (R¹—X), which is then reacted with HS⁻ or R²S⁻ to give a compound,where R¹ is to represent SH or SR².

When R¹ is to represent a hydrocarbon group, reaction takes place withR₂ ¹LiCu (R¹ representing a hydrocarbon group) to give a final compound,where R¹ then represents a hydrocarbon group.

In the same way, the compound where R¹ represents a halogen can reactwith CN⁻ to give a final compound, where R¹ will represent CN.

In addition, the compound where R¹ represents CN can, by controlledhydrolysis, give a compound where R¹ will represent CONH₂. The compoundwhere R¹ represents CN can, by complete hydrolysis, give a compoundwhere R¹ will represent COOH.

The compound where R¹ represents COOH can, by esterification, give acompound where R¹ will represent COOR².

The compound where R¹ represents COOH can react on NHR²R³ in thepresence of DCC (dicyclohexylcarbodiimide) to give a compound where R1will represent NR²R³.

The cyclodextrin derivatives according to the invention have numerousadvantages. In particular, when they are persubsituted, i.e. when allthe R¹ are different from the OH group, the derivatives have a goodsolubility in organic solvents, such as chloroform, acetone,tetrahydrofuran, etc. This solubility is of interest for their use inionic separation, because it makes it possible to carry out theseparation by liquid-liquid exchange processes, which are well known inthe art.

Moreover, the possibility of introducing one or more particular chemicalgroups makes it possible to make to measure complexing agents for veryvaried ions. This is increased by the fact that the three naturalcyclodextrins usable as a starting material, have different cavitydiameters, which can lead to a supplementary selection relative to thesize of the ions to be separated.

The starting products of formulas (III) or (IV) used in the inventioncan be prepared by conventional processes, such as those described inthe aforementioned documents 1 and 2 of Gadelle A. et al. and Ashthon P.R. et al.

Other features and advantages of the invention can be better gatheredfrom studying the following examples, given in an illustrative andnon-limitative manner with reference to the attached drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1(a), 1(b) and 1(c) are nuclear magnetic resonance (NMR) spectraof the proton of the derivative of example 1 alone (a), or in thepresence of 1 mmole/l of lead nitrate or in the presence of 3 mmole/l oflead nitrate.

DETAILED DESCRIPTION OF EMBODIMENTS EXAMPLE 1 Preparation of Hexakis(3,6-Anhydro-2-0-methyl)cyclomaltohexaose

This compound complies with the above formula (I), in which all the R¹represent OCH₃ and n is equal to 6.

Weighing takes place of 50 mg (0.057 mmole) of hexakis(3,6-anhydro)cyclomaltohexaose, dried in vacuo at 120° C. for 48 hoursand 10 ml of anhydrous dimethyl formamide (DMF) are added thereto andthe solution is heated for 15 minutes at 70° C. until a dispersion isobtained. 82 mg of sodium hydride dispersed in oil are weighed inanother flask and to the same are added 10 ml of anhydrous DMF.Accompanied by stirring, to the latter flask and using a syringe isadded the hexakis (3,6-anhydro)cyclomaltohexaose suspension. Afterstirring for 25 minutes, 200 ul of methyl iodide CH₃I (3 mmole) areadded with the syringe. After stirring for 15 minutes, the solvent isevaporated and the residue dissolved in water. The solution is washedwith chloroform in order to eliminate the oils and the aqueous part islyophilized. The latter undergoes chromatography on a polyamine PBMNcolumn manufactured by Y.M.C. using a gradient of 0 to 30% water inacetonitrile and characterized by nuclear magnetic resonance of theproton at 500 MHz, a temperature of 298 K and a concentration of 3mmole/l in D₂O.

The results obtained are shown in FIG. 1(a).

EXAMPLE 2 Formation of the Lead Complex

To an aqueous solution of the permethyl derivative obtained in example 1is added an aqueous lead nitrate solution in order to obtain an aqueoussolution containing 3 mmole/l of permethyl derivative and 1 mmole/l oflead nitrate. The solution obtained is analyzed by nuclear magneticresonance under the same conditions as in example 1 (500 MHz, D₂O, 298K).

The results obtained are given in FIG. 1(b).

In this case, the exchange is sufficiently slow compared with the NMRobservation time, to observe the two signals corresponding to the freecyclodextrin (FIG. 1(a)) and to the complex (FIG. 1(b)). The respectivesurfaces of the free and complexed parts represent 2 for 1, whichsignifies that all the lead present is complexed.

In FIG. 1(b), a clear separation between the free and complexedcyclodextrin is visible for proton H₁ only. The widening of the signalsis characteristic of a slow exchange.

EXAMPLE 3 Formation of a Lead Complex

The same operating procedure as in example 2 is followed, but theaqueous solution incorporates 3 mmole/l of the permethyl derivative ofexample 1 and 3 mmole/l of lead nitrate.

The NMR spectrum of the proton is shown in FIG. 1(c).

Here again, only the signals of the complex are visible. A singlewidened signal is observed for H1. Such a behaviour can be observed foran extremely high affinity constant.

EXAMPLE 4 Formation of the Lead Complex

The same operating procedure as in example 3 is followed, but additionalso takes place of sodium nitrate so as to obtain an aqueous solutionincorporating 3 mmole/l of the permethyl derivative of example 1, 3mmole/l of lead nitrate and 3 mmole/l of sodium nitrate.

The NMR spectrum of the complex obtained is identical to that shown inFIG. 1(c).

Thus, the NMR spectrum of the complex is not modified by the presence of3 mM sodium nitrate. This result is of vital importance with a view toapplications in the biological field, because it shows that the lead canbe complexed, even in the presence of an excess of sodium ions.

The NMR results obtained in examples 2 to 4 show that the affinityconstant of the permethyl derivative of example 1 for Pb is much higherthan that obtained with the starting hexakis(3,6-anhydro)cyclomaltohexaose, the latter being approximately 10⁵ inthe case of the permethyl derivative and approximately 2500 in the caseof the starting per(anhydro)cyclodextrin.

Thus, said permethyl derivative is of great interest, particularly forlead decontamination in living beings.

Thus, it is neither toxic, nor hemolytic, whereas the correspondingunmethylated per(3,6-anhydro)cyclodextrin is hemolytic. Moreover, it cancomplex lead, even in the presence of high sodium contents.

LIST OF CITED DOCUMENTS

Document 1: Gadelle A. and Defaye J., Angew. Chem. Int. Ed. Engl. 1991,30, pp 79—79.

Document 2: Ashton P. R., Ellwood P., Staton I. and Stoddart J. F.,Angew. Chem. Int. Ed. Engl. 1991, 30, pp 80-81.

Document 3: Yamamura H. and Fujita K., Chem. Pharm. Bull., 1991, 39, pp2505-2508.

Document 4: Yamamura H., Esuka T., Kawase Y., Kawai M., Butsugan Y. andFujita K., J. Chem. Soc., Chem. Commun., 1993, pp 636-637.

Document 5: Yamamura H., Nagaoka H., Kawai M. and Butsugan Y.,Tetrahedron Lett., 1995, 3b, pp 1093-1094.

Document 6: Ashton et al, J. Org. Chem. 1995, 60, pp 3898-3903.

What is claimed is:
 1. Derivative of per(3,6-anhydro)cyclodextrincomplying with one of the following formulas:

in which at least one of the R¹ represents the methoxy group and theother R¹, which can be the same or different, represent a groupcomplying with one of the formulas: OH, OR², SH, SR², OCOR². NH₂, NR²R³,CONR²R³, CONH₂ CN, COOR², COOH and R², in which R² represents asaturated or unsaturated, aliphatic or aromatic hydrocarbon group, whichcan have one or more heteroatoms chosen from among O, S and N, and R³represents a hydrogen atom or a saturated or unsaturated, aliphatic oraromatic, hydrocarbon group, which can have one or more heteroatomschosen from among O, S and N, and n is equal to 6, 7 or 8, provided thatall the R¹ do not represent OCH₃ when n=7 and that the derivativecomplies with formula (I).
 2. Derivative of per(3,6-anhydro)cyclodextrinaccording to claim 1 complying with formula (I), in which all the R¹represents the OCH₃ group and n is equal to
 6. 3. Complex of lead and aderivative of per(3,6-anhydro)cyclodextrin complying with one of thefollowing formulas:

in which at least one of the R¹ represents the methoxy group and theother R¹, which can be the same or different, represent a groupcomplying with one of the formulas: OH, OR², SH, SR², OCOR². NH₂, NR²R³,CONR²R³, CONH₂ CN, COOR², COOH and R², in which R² represents asaturated or unsaturated, aliphatic or aromatic hydrocarbon group, whichcan have one or more heteroatoms chosen from among O, S and N, and R³represents a hydrogen atom or a saturated or unsaturated, aliphatic oraromatic, hydrocarbon group, which can have one or more heteroatomschosen from among O, S and N, and n is equal to 6, 7 or
 8. 4. Complexaccording to claim 3, wherein n is equal to
 6. 5. Complex according toclaim 3, wherein the per(3,6-anhydro)cyclodextrin derivative complieswith formula (I), in which all the R¹ represent the methoxy group and nis equal to
 6. 6. Process for the fixation or separation of lead ions,which comprises contacting a medium containing said lead ions with aderivative of per(3,6-anhydro)cyclodextrin, complying with one of thefollowing formulas:

in which at least one of the R¹ represents the methoxy group and theother R¹, which can be the same or different, represent a groupcomplying with one of the formulas: OH, OR², SH, SR², OCOR². NH₂, NR²R³,CONR²R³, CONH₂ CN, COOR², COOH and R², in which R² represents asaturated or unsaturated, aliphatic or aromatic, hydrocarbon group,which can have one or more heteroatoms chosen from among O, S and N, andR³ represents a hydrogen atom or a saturated or unsaturated, aromatic oraliphatic, hydrocarbon group, which can have one or more heteroatomschosen from among O, S and N, and n is equal to 6, 7 or 8, for fixingsaid lead ions in complex form with the per(3,6-anhydro)cyclodextrinderivative and for separating them from said medium.
 7. Processaccording to claim 6, wherein n is equal to
 6. 8. Process according toclaim 6, wherein the per(3,6-anhydro)cyclodextrin derivative complieswith formula (I), in which all the R¹ represent the methoxy group and nis equal to
 6. 9. Process according to claim 6 wherein said medium is anaqueous solution, the cyclodextrin derivative being dissolved in anorganic solvent immiscible with the aqueous solution.
 10. Process oflead decontamination of an animal which comprises the step ofadministering to an animal in need of lead decontamination apharmaceutical composition comprises a per(3,6-anhydro)cyclodextrinderivative complying with one of the following formulas:

in which at least one of the R¹ represents the methoxy group and theother R¹, which can be the same or different, represent a groupcomplying with one of the formulas: OH, OR², SH, SR², OCOR², NH₂, NR²R³,CONR²R³, CONH₂, CN, COOR², COOH and R², in which R² represents asaturated or unsaturated, aliphatic or aromatic, hydrocarbon group,which can have one or more heteroatoms chosen from among O, S and N, andR³ represents a hydrogen atom or a saturated or unsaturated, aliphaticor aromatic, hydrocarbon group, which can have one or more heteroatomschosen from among O, S and N, and n is equal to 6, 7 or
 8. 11. Theprocess of claim 10 wherein the per(3,6-anhydro)cyclodextrin derivativecomplies with formula (I), in which all the R¹ represent the methoxygroup and n is equal to 6.